To provide an attaching and detaching mechanism attachable in a space saving manner while reducing labor during attachment and detachment, and to provide a game machine provided with a fixing mechanism.

When a lock pin 20 is inserted into a lock pin insertion hole 32 provided on a main shaft 30, a lock spring 42 of a fixing member 40 arranged on a side face of the main shaft 30 is engaged with a locking groove 22 provided on a side face of the lock pin 20. At the time, since a release ring 50 is moved along a side face of the fixing member 40 to regulate the movement of the lock spring 42 in the direction of separating from the fixing member 40, the engaged state of the locking groove 22 and the lock spring 42 is prevented from being released. In other words, since the lock pin 20 having the locking groove 22 and the fixing member 40 having the lock spring 42 can be kept in a fixed state, the lock pin 20 is fixed to the main shaft 30 by an easy operation of inserting the lock pin 20 into the lock pin insertion hole 32.